The overall objective of the grant is to determine the importance of bacterial inoculum size and amniotic fluid bacterial growth inhibitors in the development of acute intra-amniotic infection. In a relatively homogeneous population, we are comparing quantitative cultures of amniotic fluid and frequency of inhibitors in an infected group and in an uninfected matched control group. In the initial year (ending November 1980), our goals have been to (1) collect amniotic fluid specimens for culture and chemistry tests from the infected and control groups, and (2) standardize the assay for amniotic fluid inhibitory activity against E. coli (06) and Group B streptococci (serotype III). Studies to date: Since November 1, 1979, we have collected fluid from 65 control patients and 40 patients with possible intraamniotic infection. We have been able to match successfully 29 patients with a firm clinical diagnosis of intra-amniotic infection with 29 patients without infection. Of the 29 specimens from infected patients, 25 (86%) had greater than 10 to 3rd power colony forming units (CFU)/ml while of the 29 controls, 8 (28%) had greater than 10 to 3rd power CFU/ml (p less than .01). The assay for inhibitory activity against E. coli has been fully developed, standardized, and tested for reproducibility. In testing fluid from control patients, we have found the reproducibility to be greater than 95% when samples were tested in duplicate on the same day or when they were tested on different days. We have recently started performing the inhibitory assay on paired specimens. We have determined the zinc concentration of 42 amniotic fluid samples and find the range to be 0.071 to 1.330 microgram ml.